Add initial shadow realm support behind an off-by-default flag
`--experimental-shadow-realm`.

PR-URL: nodejs#42869
Refs: nodejs#42528
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>

According to https://html.spec.whatwg.org/#environment-settings-object,
the timeOrigin is a per-environment value. Worker's timeOrigin is the
time when the worker is created.

PR-URL: nodejs#43781
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Paolo Insogna <paolo@cowtech.it>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>

This patch updates the layout of the BaseObjects to make sure
that the first embedder field of them is a "type" pointer, the
first 16 bits of which are the Node.js embedder ID, so that
cppgc will always skip over them. In addition we now use this
field to determine if the native object should be interpreted
as a Node.js embedder object in the serialization and deserialization
callbacks for the startup snapshot to improve the reliability.

Co-authored-by: Joyee Cheung <joyeec9h3@gmail.com>
PR-URL: nodejs#43521
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>

This patch stores the metadata about the Node.js binary
into the SnapshotData and adds fields denoting how the
snapshot was generated, on what platform it was
generated as well as the V8 cached data version flag.
Instead of simply crashing when the metadata doesn't
match, Node.js now prints an error message and exit with
1 for the customized snapshot, or ignore the snapshot
and start from scratch if it's the default one.

PR-URL: nodejs#44132
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>

Instead of iterating over the bindings, iterate over the base
objects that are snapshottable. This allows us to snapshot
base objects that are not bindings. In addition this refactors
the InternalFieldInfo class to eliminate potential undefined
behaviors, and renames it to InternalFieldInfoBase.
The {de}serialize callbacks now expect a InternalFieldInfo struct
nested in Snapshotable classes that can be used to carry
serialization data around. This allows us to create structs
inheriting from InternalFieldInfo for Snapshotable objects
that need custom fields.

PR-URL: nodejs#44192
Refs: nodejs#37476
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>

Move util::WeakReference to a separate header and implement
{de}serialization for it to be snapshotable.

PR-URL: nodejs#44193
Refs: nodejs#44014
Refs: nodejs#37476
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>

To distinguish per-context values from the node::Environment, split
those values to a new node::Realm structure and consolidate
bootstrapping methods with it.

PR-URL: nodejs#44179
Refs: nodejs#42528
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

BaseObject is a wrapper around JS objects. These objects should be
created in a node::Realm and destroyed when their associated realm is
cleaning up.

PR-URL: nodejs#44348
Refs: nodejs#42528
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>

- Wrap the initialization of the kSlot and kEmbedderType fields
  into a BaseObject::SetInternalFields() method.
- Move the tagging of kEmbedderType field into
  BaseObject::TagNodeObject()
- Add a variant of BaseObject::MakeLazilyInitializedJSTemplate()
  that only needs IsolateData.
This makes it easier to create BaseObject subclasses.

PR-URL: nodejs#44796
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

PR-URL: nodejs#44796
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Instead of adding a reference to the ContextifyContext by using
a v8::External, we make ContextifyContext a weak BaseObject that
whose wrapper is referenced by the sandbox via a private symbol.
This makes it easier to snapshot the contexts, in addition to
reusing the BaseObject lifetime management for ContextifyContexts.

PR-URL: nodejs#44796
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>